In the quest to bring new sources of hydrocarbons such as crude oil and natural gas to market, the Arctic Ocean and other ice prone areas are among the few areas where large reserves of such hydrocarbons are believed to be found. A majority of arctic offshore oil and gas reserves in the arctic are found at locations where the moving ice is multi-year ice, i.e. ice that did not melt during the summer following its formation and has become compacted and harder during the subsequent years. The hazards of exploring, drilling and producing in such environments are generally recognized, but cost effective solutions are not readily available. It is commonly known in the industry that costs for bringing hydrocarbon resources to market are considerably higher when the resources are either offshore versus onshore or in a remote or harsh environment versus a hospitable, non-arctic, and populated location. In offshore arctic projects, costs are astronomically higher due to the combination of all those factors and preparations for contending with multi-year ice increases costs even further.
One area of the significant cost components in an arctic offshore development project is the cost of the platform that is suitable to resist the forces exerted by multi-year ice floes. Current conventional technology comprises Gravity-Based-Structures or GBS which are huge steel or reinforced concrete structures that are floated from the fabrication site to the development location and lowered to the seafloor. High specific gravity minerals, e.g. Hematite (Iron ore mineral), or metal pellets are used to fill the compartments within the GBS until the total weight of the structure is sufficient to resist any sliding and overturning forces the moving ice floe might impose on it. It is conventional to provide the GBS with sloped perimeter surfaces so that as ice engages the structure, the ice slides upwards to bend and break along the slope surfaces. The ice is effectively turned away from the GBS although significant pressure can be created by ice, especially from multi-year ice that may exceed twenty meters in thickness.
Typically, a GBS is quite a bit wider than it is tall. Currently, a conventional GBS costs between 500 million to more than a billion US dollars depending on the water depth, number of drillings rigs supported on the platform, and the thickness of the expected multi-year ice. Seafloor preparation is a considerable expense item which typically comprises the extensive removal of soft and muddy materials directly beneath the base of the GBS and replacing it with hundreds of thousands of tons of gravel to form a firm, level gravel bed for the GBS to be safely supported without permitting much settlement. In some circumstances, especially when the water depth is deeper than 20 meters, design considerations include building up the seabed or building a taller GBS, and each alternative is quite expensive. The size of the GBS and costs for installing one at an ice-prone offshore location makes the GBS suitable only for fields that are proven to have very large reserves and that have high production rates. The cost of a GBS can be prohibitive if there is a substantially thick layer of very soft soils that must be replaced with well compacted granular material to ensure safe and adequate bearing strength of the soil upon which the GBS will be supported. There are or will be fields that could be significant producers of oil and natural gas that are not large enough to justify the enormous cost of a GBS.